To improve channel conductivity of a transistor by increasing carrier mobility in a channel region of the transistor, strain is created in the channel region to generate tensile or compressive stress. In a channel region of a p-type metal-oxide-semiconductor (PMOS) transistor, compressive stress is generated to increase mobility of holes, and in a channel region of an n-type metal-oxide-semiconductor (NMOS) transistor, tensile stress is generated to increase mobility of electrons.
In a complementary-metal-oxide-semiconductor (CMOS) transistor, in order to form a stress creating layer in recessed source and drain areas of a PMOS transistor, a blocking layer for masking an NMOS transistor needs to be formed. Thus, a photolithography process for forming the blocking layer is required. When removing the blocking layer after forming the stress creating layer, residues exist in the blocking layer and the device characteristics of the CMOS transistor are deteriorated. Also, leakage characteristics of the NMOS transistor are deteriorated due to an etching difference occurring when forming a tensile stress creating layer in the NMOS transistor.